The first creation of the title Baron Sydney was extinct with the death of the 7th Earl of Leicester in 1743.

In 1768, Dudley Cosby, Minister Plenipotentiary to Denmark between 1763 and 1765, was made Baron Sydney (second creation), of Stradbally in the Queen's County, in the Peerage of Ireland. This creation became extinct on Lord Sydney's death in 1774.

Elizabeth, daughter and heiress of Thomas Sidney, fourth son of Robert Sidney, 4th Earl of Leicester, was the grandmother of John Shelley-Sidney, whose son Philip Sidney (1800–1851) was raised to the Peerage of the United Kingdom as Baron De L'Isle and Dudley. His successors also carried the surname Sidney:

Sidney became widely used as a given name in English speaking countries during the 19th century, with much of its use in the United States after the American Revolution being due to admiration for Algernon Sidney as a martyr to royal tyranny.[3] People with this given name born in the United States during the 19th century include Sidney Lanier (1842–1881) and Sidney Homer (1864–1953).
Use as a male given name in the United States peaked in the 1910s and has declined steadily since. There has been a recent fashion since the early 1990s of giving the name Sidney to girls. This trend peaked in the late 1990s and has declined during the 2000s.[4]

^Hanks, P. & Hodges, F. (1988). A dictionary of surnames. Oxford University Press, New York, ISBN0-19-211592-8. "The name is usually derived from St. Denis but proof is lacking". Reaney, P.H. & Wilson, R.M. (1997)

^Karsten, Peter (1978) Patriot heroes in England and America: Political symbolism and changing values over three centuries University of Wisconsin Press, Madison ISBN0-299-07500-1

This page lists people with the surnameSidney. If an internal link intending to refer to a specific person led you to this page, you may wish to change that link by adding the person's given name(s) to the link.